In-vitro and in-vivo studies of PLA / PCL / gelatin composite scaffold containing ascorbic acid for bone regeneration

Magnesium-oxide-enhanced bone regeneration: 3D-printing of gelatin-coated composite scaffolds with sustained Rosuvastatin release

Critical-size bone defects are one of the main challenges in bone tissue regeneration that determines the need to use angiogenic and osteogenic agents. Rosuvastatin (RSV) is a class of cholesterol-lowering drugs with osteogenic potential. Magnesium oxide (MgO) is an angiogenesis component affecting apatite formation. This study aims to evaluate 3D-printed Polycaprolactone/β-tricalcium phosphate/nano-hydroxyapatite/ MgO (PCL/β-TCP/nHA/MgO) scaffolds as a carrier for MgO and RSV in bone regeneration. For this purpose, PCL/β-TCP/nHA/MgO scaffolds were fabricated with a 3D-printing method and coated with gelatin and RSV. The biocompatibility and osteogenicity of scaffolds were examined with MTT, ALP, and Alizarin red staining. Finally, the scaffolds were implanted in a bone defect of rat's calvaria, and tissue regeneration was investigated after 3 months. Our results showed that the simultaneous presence of RSV and MgO improved biocompatibility, wettability, degradation rate, and ALP activity but decreased mechanical strength. PCL/β-TCP/nHA/MgO/gelatin-RSV scaffolds produced sustained release of MgO and RSV within 30 days. CT images showed that PCL/β-TCP/nHA/MgO/gelatin-RSV scaffolds filled approximately 86.83 + 4.9 % of the defects within 3 months and improved angiogenesis, woven bone, and osteogenic genes expression. These results indicate the potential of PCL/β-TCP/nHA/MgO/gelatin-RSV scaffolds as a promising tool for bone regeneration and clinical trials.

Evaluating osteogenic effects associated with the incorporation of ascorbic acid in mineralized collagen scaffolds

Current treatments for craniomaxillofacial (CMF) defects motivate the design of instructive biomaterials that can promote osteogenic healing of complex bone defects. We report methods to promote in vitro osteogenesis of human mesenchymal stem cells (hMSCs) within a model mineralized collagen scaffold via the incorporation of ascorbic acid (vitamin C), a key factor in collagen biosynthesis and bone mineralization. An addition of 5 w/v% ascorbic acid into the base mineralized collagen scaffold significantly changes key morphology characteristics including porosity, macrostructure, and microstructure. This modification promotes hMSC metabolic activity, ALP activity, and hMSC-mediated deposition of calcium and phosphorous. Additionally, the incorporation of ascorbic acid influences osteogenic gene expression (BMP-2, RUNX2, COL1A2) and delays the expression of genes associated with osteoclast activity and bone resorption (OPN, CTSK), though it reduces the secretion of OPG. Together, these findings highlight ascorbic acid as a relevant component for mineralized collagen scaffold design to promote osteogenic differentiation and new bone formation for improved CMF outcomes.

Exploring the Biomedical Potential of PLA/Dysprosium Phosphate Composites via Extrusion-Based 3D Printing: Design, Morphological, Mechanical, and Multimodal Imaging and Finite Element Modeling

The present investigation demonstrates the feasibility of dysprosium phosphate (DyPO4) as an efficient additive in polylactide (PLA) to develop 3D printed scaffolds through the material extrusion (MEX) principle for application in bone tissue engineering. Initially, uniform sized particles of DyPO4 with tetragonal crystal setting are obtained and subsequently blended with different concentrations of PLA to extrude in the form of filaments. A maximum of 20 wt % DyPO4 in PLA matrix has been successfully drawn to yield a defect free filament. The resultant filaments were 3D printed through material extrusion methodology. The structural and morphological analysis confirmed the successful reinforcement of DyPO4 throughout the PLA matrix in all of the 3D printed components. All of the PLA/DyPO4 composites exhibited magnetic resonance imaging and computed tomography contrasting properties, which were dependent on the dysprosium content in the PLA matrix. The detailed mechanical evaluation of the 3D printed PLA/DyPO4 composites ensured good strength accomplished by the reinforcement of 5 wt % DyPO4 in PLA matrix, beyond which a gradual decline in the strength is noticed. Representative volume elements models were developed to realize the intrinsic property of the PLA/DyPO4 composite, and finite element analysis under both static and dynamic loading conditions has been performed to account for the reliability of experimental results.

An ascorbic acid-decorated nanostructured surface on titanium inhibits breast cancer development and promotes osteogenesis

The chest wall is the most frequent metastatic site of breast cancer (BC) and the metastasis usually occurs in a solitary setting. Chest wall resection is a way to treat solitary BC metastasis, but intraoperative bone defects and local tumor recurrence still affect the life quality of patients. Titanium-based prostheses are widely used for chest wall repair and reconstruction, but their inherent bio-inertness makes their clinical performance unfavorable. Nanostructured surfaces can give titanium substrates the ability to excellently modulate a variety of cellular functions. Ascorbic acid is a potential stimulator of tumor suppression and osteogenic differentiation. An ascorbic acid-decorated nanostructured titanium surface was prepared through alkali treatment and spin-coating technique and its effects on the biological responses of BC cells and osteoblasts were assessed. The results exhibited that the nanorod structure and ascorbic acid synergistically inhibited the proliferation, spreading, and migration of BC cells. Additionally, the ascorbic acid-decorated nanostructured surface significantly promoted the proliferation and osteogenic differentiation of osteoblasts. This work may provide valuable references for the clinical application of titanium materials in chest wall reconstruction after the resection of metastatic BC.

Bioactive Scaffolds as a Promising Alternative for Enhancing Critical-Size Bone Defect Regeneration in the Craniomaxillofacial Region

Reconstruction of critical-size bone defects (CSDs) in the craniomaxillofacial (CMF) region remains challenging. Scaffold-based bone-engineered constructs have been proposed as an alternative to the classical treatments made with autografts and allografts. Scaffolds, a key component of engineered constructs, have been traditionally viewed as biologically passive temporary replacements of deficient bone lacking intrinsic cues to promote osteogenesis. Nowadays, scaffolds are functionalized, giving rise to bioactive scaffolds promoting bone regeneration more effectively than conventional counterparts. This review focuses on the three approaches most used to bioactivate scaffolds: (1) conferring microarchitectural designs or surface nanotopography; (2) loading bioactive molecules; and (3) seeding stem cells on scaffolds, providing relevant examples of in vivo (preclinical and clinical) studies where these methods are employed to enhance CSDs healing in the CMF region. From these, adding bioactive molecules (specifically bone morphogenetic proteins or BMPs) to scaffolds has been the most explored to bioactivate scaffolds. Nevertheless, the downsides of grafting BMP-loaded scaffolds in patients have limited its successful translation into clinics. Despite these drawbacks, scaffolds containing safer, cheaper, and more effective bioactive molecules, combined with stem cells and topographical cues, remain a promising alternative for clinical use to treat CSDs in the CMF complex replacing autografts and allografts.

Osteocyte-Like Cells Differentiated From Primary Osteoblasts in an Artificial Human Bone Tissue Model

In vitro models of primary human osteocytes embedded in natural mineralized matrix without artificial scaffolds are lacking. We have established cell culture conditions that favored the natural 3D orientation of the bone cells and stimulated the cascade of signaling needed for primary human osteoblasts to differentiate into osteocytes with the characteristically phenotypical dendritic network between cells. Primary human osteoblasts cultured in a 3D rotating bioreactor and incubated with a combination of vitamins A, C, and D for up to 21 days produced osteospheres resembling native bone. Osteocyte-like cells were identified as entrapped, stellate-shaped cells interconnected through canaliculi embedded in a structured, mineralized, collagen matrix. These cells expressed late osteoblast and osteocyte markers such as osteocalcin (OCN), podoplanin (E11), dentin matrix acidic phosphoprotein 1 (DMP1), and sclerostin (SOST). Organized collagen fibrils, observed associated with the cell hydroxyapatite (HAp) crystals, were found throughout the spheroid and in between the collagen fibrils. In addition to osteocyte-like cells, the spheroids consisted of osteoblasts at various differentiation stages surrounded by a rim of cells resembling lining cells. This resemblance to native bone indicates a model system with potential for studying osteocyte-like cell differentiation, cross-talk between bone cells, and the mineralization process in a bonelike structure in vitro without artificial scaffolds. In addition, natural extracellular matrix may allow for the study of tissue-specific biochemical, biophysical, and mechanical properties. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

3D bioprinting of dECM/Gel/QCS/nHAp hybrid scaffolds laden with mesenchymal stem cell-derived exosomes to improve angiogenesis and osteogenesis

Craniofacial bone regeneration is a coupled process of angiogenesis and osteogenesis, which, associated with infection, still remains a challenge in bone defects after trauma or tumor resection. 3D tissue engineering scaffolds with multifunctional-therapeutic properties can offer many advantages for the angiogenesis and osteogenesis of infected bone defects. Hence, in the present study, a microchannel networks-enriched 3D hybrid scaffold composed of decellularized extracellular matrix (dECM), gelatin (Gel), quaterinized chitosan (QCS) and nano-hydroxyapatite (nHAp) (dGQH) was fabricated by an extrusion 3D bioprinting technology. And enlightened by the characteristics of natural bone microstructure and the demands of vascularized bone regeneration, the exosomes (Exos) isolated from human adipose derived stem cells as angiogenic and osteogenic factors were then co-loaded into the desired dGQH₂₀hybrid scaffold based on an electrostatic interaction. The results of the hybrid scaffolds performance characterization showed that these hybrid scaffolds exhibited an interconnected pore structure and appropriate degradability (>61% after 8 weeks of treatment), and the dGQH₂₀hybrid scaffold displayed the highest porosity (83.93 ± 7.38%) and mechanical properties (tensile modulus: 62.68 ± 10.29 MPa, compressive modulus: 16.22 ± 3.61 MPa) among the dGQH hybrid scaffolds. Moreover, the dGQH₂₀hybrid scaffold presented good antibacterial activities (against 94.90 ± 2.44% ofEscherichia coliand 95.41 ± 2.65% ofStaphylococcus aureus, respectively) as well as excellent hemocompatibility and biocompatibility. Furthermore, the results of applying the Exos to the dGQH₂₀hybrid scaffold showed that the Exo promoted the cell attachment and proliferation on the scaffold, and also showed a significant increase in osteogenesis and vascularity regeneration in the dGQH@Exo scaffoldsin vitroandin vivo. Overall, this novel dECM/Gel/QCS/nHAp hybrid scaffold laden with Exo has a considerable potential application in reservation of craniofacial bone defects.

Detection of Limbal Stem Cells Adhered to Melt Electrospun Silk Fibroin and Gelatin-Modified Polylactic Acid Scaffolds

Limbal stem cells (LSCs) are of paramount importance in corneal epithelial tissue repair. The cornea becomes opaque in case of limbal stem cell deficiency (LSCD), which may cause serious damage to the ocular visual function. There are many techniques to restore damaged epithelium, one of which is the transplantation of healthy cultured LSCs, usually onto a human amniotic membrane or onto bio-based engineered scaffolds in recent years. In this study, melt electrospun polylactic acid (PLA) was modified by silk fibroin or gelatin and further cultured with LSCs originating from three different donors. In terms of physicochemical properties, both modifications slightly increased PLA scaffold porosity (with a significantly larger pore area for the PLA/gelatin) and improved the scaffolds' swelling percentage, as well as their biodegradation rate. In terms of the scaffold application function, the aim was to detect/visualize whether LSCs adhered to the scaffolds and to further determine cell viability (total number), as well as to observe p63 and CK3 expressions in the LSCs. LSCs were attached to the surface of microfibers, showing flattened conformations or 3D spheres in the formation of colonies or agglomerations, respectively. All scaffolds showed the ability to bind the cells onto the surface of individual microfibers (PLA and PLA/gelatin), or in between the microfibers (PLA/silk fibroin), with the latter showing the most intense red fluorescence of the stained cells. All scaffolds proved to be biocompatible, while the PLA/silk fibroin scaffolds showed the highest 98% viability of 2.9 × 10⁶ LSCs, with more than 98% of p63 and less than 20% of CK3 expressions in the LSCs, thus confirming the support of their growth, proliferation and corneal epithelial differentiation. The results show the potential of these bio-engineered scaffolds to be used as an alternative clinical approach.

Preparation of porous PCL-PEG-PCL scaffolds using supercritical carbon dioxide

In this study, the Supercritical Carbon Dioxide (scCO₂) gas foaming procedure was used in the preparation of scaffolds containing the model drug dexamethasone (DXMT). The method used did not include an organic solvent thus making it a safe method. The ring-opening polymerization of PCL-PEG-PCL (PCEC) triblock was conducted using an organocatalyst [1,8 diazabicyclo [5.4.0] undec-7-ene (DBU)]. After mixing 5.0 g of DXMT with 50.0 g of PCEC, hydraulic pressure was applied to compress the mixed powder into disc-like tablets. The tablet-like scaffold of the triblock containing DXMT was inserted into a scCO₂ gas-foaming device. The peak porosity percentage of the synthesized triblock was found to be 55.58 %. Pressure, temperature, soaking time and the time required to depressurize were recorded as 198 bar, 50 °C, 2.0 h, and 28 min respectively. After treatment with scCO₂, the scaffolds experienced an almost full release of DXMT in vitro after 30 days (83.74 ± 1.54 % vs 52.24 ± 2.03 % before scCO₂ treatment). In conclusion, the results proved that the scCO₂ gas foaming procedure could be employed for constructing modifiable PCEC scaffolds with plausible porosity and structural and morphological features which can manipulate drug release.

Physico-mechanical and in-vivo evaluations of tri-layered alginate-gelatin/polycaprolactone-gelatin-β-TCP membranes for guided bone regeneration

Guided bone regeneration (GBR) membranes favor periodontal regrowth, but they still have certain limitations, such as improper biodegradation and poor mechanical property. To overcome these shortcomings, we have generated a unique multifunctional membrane. A polycaprolactone/gelatin/β-TCP and alginate/gelatin trilayered construction was fabricated through electrospinning and casting technology. The prepared membranes have suitable physicomechanical and in-vitro properties to confirm the compatibility of the product in the body. Phase analysis, functional groups, surface microstructure, and contact angle were measured as basic characteristics. For a mechanical performance evaluation, the tensile strength at suturing point was measured through pullout tensile strength test, and it showed the suture capability of bi-layered membranes. Highest tensile strength for A75G25 was recorded with 2.9 ± 0.15 MPa with 105% strain. Further, the osteoblast and fibroblast-type cell toxicity results showed that the electrospun membrane offered compatible environment to cells while the alginate sheet was found to be sufficiently capable to suppress the cellular attachment while also being a nontoxic material. Post-implantation, according to the in-vivo conclusions of the tri-layered membrane, there was appreciable bone formation. Compared to an implant without membrane covering, enhanced new bone formation can be identified after 8 weeks of implantation with P1G4β10 membranes-covered site.

Gelatin-based electrospun and lyophilized scaffolds with nano scale feature for bone tissue engineering application: review

The rebuilding of the normal functioning of the damaged human body bone tissue is one of the main objectives of bone tissue engineering (BTE). Fabricated scaffolds are mostly treated as artificial supports and as materials for regeneration of neo bone tissues and must closely biomimetic the native extracellular matrix of bone. The materials used for developing scaffolds should be biodegradable, nontoxic, and biocompatible. For the resurrection of bone disorder, specifically natural and synthetic polymers such as chitosan, PCL, gelatin, PGA, PLA, PLGA, etc. meet the requirements for serving their functions as artificial bone substitute materials. Gelatin is one of the potential candidates which could be blended with other polymers or composites to improve its physicochemical, mechanical, and biological performances as a bone graft. Scaffolds are produced by several methods including electrospinning, self-assembly, freeze-drying, phase separation, fiber drawing, template synthesis, etc. Among them, freeze-drying and electrospinning are among the popular, simplest, versatile, and cost-effective techniques. The design and preparation of freeze-dried and electrospun scaffolds are of intense research over the last two decades. Freeze-dried and electrospun scaffolds offer a distinctive architecture at the micro to nano range with desired porosity and pore interconnectivity for selective movement of small biomolecules and play its role as an appropriate matrix very similar to the natural bone extracellular matrix. This review focuses on the properties and functionalization of gelatin-based polymer and its composite in the form of bone scaffolds fabricated primarily using lyophilization and electrospinning technique and their applications in BTE.

Tailored alginate/PCL-gelatin-β-TCP membrane for guided bone regeneration

Membranes prepared for guided bone regeneration (GBR) signify valued resources, inhibiting fibrosis and assisting bone regenration. However, existing membranes lack bone regenerative capacity or adequate degradation profile. An alginate-casted polycaprolactone (PCL)-gelatin-β-tricalcium phosphate (β-TCP) dual membrane was fabricated by electrospinning and casting processes to enhance new bone formation under a guided bone regeneration (GBR) process. Porous membranes were synthesized with suitable hydrophilicity, swelling, and degradation behavior to confirm the compatibility of the product in the body. Furthermore, osteoblast-type cell toxicity and cell adhesion results showed that the electrospun membrane offered compatible environment to cells while the alginate sheet was found capable enough to supress the cellular attachment, but was a non-toxic material. Post-implantation, the in-vivo outcomes of the dual-layered membrane, showed appreciable bone formation. Significantly, osteoid islands had fused in the membrane group by 8 weeks. The infiltration of fibrous tissues was blocked by the alginate membrane, and the ingrowth of new bone was enhanced. Immunocytochemical analysis indicated that the dual membrane could direct more proteins which control mineralization and convene osteoconductive properties of tissue-engineered bone grafts.

Recent Advances in Functional Polymer Materials for Energy, Water, and Biomedical Applications: A Review

Academic research regarding polymeric materials has been of great interest. Likewise, polymer industries are considered as the most familiar petrochemical industries. Despite the valuable and continuous advancements in various polymeric material technologies over the last century, many varieties and advances related to the field of polymer science and engineering still promise a great potential for exciting new applications. Research, development, and industrial support have been the key factors behind the great progress in the field of polymer applications. This work provides insight into the recent energy applications of polymers, including energy storage and production. The study of polymeric materials in the field of enhanced oil recovery and water treatment technologies will be presented and evaluated. In addition, in this review, we wish to emphasize the great importance of various functional polymers as effective adsorbents of organic pollutants from industrial wastewater. Furthermore, recent advances in biomedical applications are reviewed and discussed.

Composite P(3HB-3HV)-CS Spheres for Enhanced Antibiotic Efficiency

Natural-derived biopolymers are suitable candidates for developing specific and selective performance-enhanced antimicrobial formulations. Composite polymeric particles based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and chitosan, P(3HB-3HV)-CS, are herein proposed as biocompatible and biodegradable delivery systems for bioproduced antibiotics: bacitracin (Bac), neomycin (Neo) and kanamycin (Kan). The stimuli-responsive spheres proved efficient platforms for boosting the antibiotic efficiency and antibacterial susceptibility, as evidenced against Gram-positive and Gram-negative strains. Absent or reduced proinflammatory effects were evidenced on macrophages in the case of Bac-/Neo- and Kan-loaded spheres, respectively. Moreover, these systems showed superior ability to sustain and promote the proliferation of dermal fibroblasts, as well as to preserve their ultrastructure (membrane and cytoskeleton integrity) and to exhibit anti-oxidant activity. The antibiotic-loaded P(3HB-3HV)-CS spheres proved efficient alternatives for antibacterial strategies.

In vivo biocompatibility and biodegradability of poly(lactic acid)/poly(ε-caprolactone) blend compatibilized with poly(ε-caprolactone-b-tetrahydrofuran) in Wistar rats

Poly(lactic acid) (PLA) and poly(ɛ-caprolactone) (PCL) are two important aliphatic esters known for their biodegradability and bioresorbability properties; the former is stiffer and brittle while the smaller modulus of the latter allows a suitable elongation. The new biomaterials being developed from the blend of these two polymers (PLA and PCL) is opportune due to the reducing interfacial tension between their immiscible phases. In a previous study, PLA/PCL immiscible blend when compatibilized with poly(ε-caprolactone-b-tetrahydrofuran) resulted in enhanced ductility and toughness no cytotoxic effect in vitro tests. There is little published data on the effect of poly(ε-caprolactone-b-tetrahydrofuran) on PLA and PCL biocompatibility and biodegradability in vivo tests. This study focuses on evaluating the behavioral response and polymer-tissue interaction of compatibilized PLA/PCL blend compared to neat PLA implanted via intraperitoneal (IP) and subcutaneous (SC) in male Wistar rats, distributed in four experimental groups: neat PLA, PLA/PCL blend, sham, and control at 2-, 8- and 24-weeks post-implantation (WPI). Open-field test was performed to appraise emotionality and spontaneous locomotor activity. Histopathological investigation using hematoxylin-eosin (H&E) and picrosirius-hematoxylin (PSH) was used to assess polymer-tissue interaction. Modifications in PLA and the PLA / PCL blend's surface morphology were determined by scanning electron microscopy (SEM). PLA group defecated more often than PLA/PCL rats 2 and 8 WPI. Conjunctive capsule development around implants, cell adhesion, angiogenesis, and giant cells of a foreign body to the biomaterial was observed in light microscopy. Both groups displayed a fibrous reaction along with collagen deposition around the biomaterials. In the SEM, the images showed a higher degradation rate for the PLA/PCL blend in both implantation routes. The polymers implanted via IP exhibited a higher degradation rate compared to SC. These findings emphasize the biocompatibility of the PLA/PCL blend compatibilized with poly(ε-caprolactone-b-tetrahydrofuran), making this biopolymer an acceptable alternative in a variety of biomedical applicatio.

Progress and Prospects of Polymer-Based Drug Delivery Systems for Bone Tissue Regeneration

Despite the high regenerative capacity of bone tissue, there are some cases where bone repair is insufficient for a complete functional and structural recovery after damage. Current surgical techniques utilize natural and synthetic bone grafts for bone healing, as well as collagen sponges loaded with drugs. However, there are certain disadvantages associated with these techniques in clinical usage. To improve the therapeutic efficacy of bone tissue regeneration, a number of drug delivery systems based on biodegradable natural and synthetic polymers were developed and examined in in vitro and in vivo studies. Recent studies have demonstrated that biodegradable polymers play a key role in the development of innovative drug delivery systems and tissue engineered constructs, which improve the treatment and regeneration of damaged bone tissue. In this review, we discuss the most recent advances in the field of polymer-based drug delivery systems for the promotion of bone tissue regeneration and the physical-chemical modifications of polymers for controlled and sustained release of one or more drugs. In addition, special attention is given to recent developments on polymer nano- and microparticle-based drug delivery systems for bone regeneration.